In a projector of the digital light processing (DLP; US registered trademark of Texas Instruments Incorporated) method, a image is cast using an optical semiconductor called a DLP chip containing millions of small mirrors (micromirrors). In the case of a three-chip-type DLP method using three DLP chips, lamp light is decomposed into three primary colors of light (RGB) with a special prism, and each DLP chip is illuminated to display a color image. Meanwhile, in the case of a one-chip-type DLP method using one DLP chip, lamp light is decomposed into three primary colors of light (RGB) with one color wheel color-coded into three colors of RGB, and one DLP chip is illuminated to display a color image. Since the color wheel rotates at high speed and a micromirror is switched ON/OFF at high speed according to the rotation, the human eye sees the displayed image as a color image in which RGB is synthesized by the afterimage effect.
The digital micromirror device typified by the above-described DLP chip is common as a reflection-type image display element for a projector. The digital micromirror device has an image display surface made up of a plurality of minute micromirrors and controls the tilt of each mirror surface on the image display surface so as to modulate the intensity of illumination light, so that an image is formed. In other words, turning ON/OFF of each pixel of the digital micromirror device is implemented, for example, by revolving a mirror surface by ±12° around a rotation axis forming an angle of 45° with respect to each side of the image display surface (that is, the micromirror is driven with regard to one axis). Concerning the action of the micromirror, a digital micromirror device of a new operation type (tilt & roll pixel digital micromirror device (DMD)) that drives a micromirror with regard to two orthogonal axes is also known.
Various types of projection-type display devices have been proposed in the past as a projector equipped with a reflection-type image display element such as the above-mentioned digital micromirror device (see, for example, Patent Literature 1) and a bright high-definition projector is further required.